1. Field of the Invention
The present invention relates generally to optical aperture mechanisms and more particularly to a mechanism including multiple selectable and rotatable pattern apertures.
2. Discussion of the Prior Art
Conventional theatrical and display lighting systems have used various types of optical filters which are removably insertable into light beams to modify the distribution of light in the projected beam. U.S. Pat. No. 2,214,728 describes a color wheel which includes several optical filters and which is rotatable to position a selected filter across a beam of light. The several filters have equal areas with uniformly dense coloring and do not produce different shapes in the projected beam of light.
U.S. Pat. No. 1,449,122 describes a kaleidoscope projector including several hollow tubes that are lined with different numbers of mirrors and supported in a frame which is rotatable to position a selected tube around light in a beam along an optical axis. Tube rotation gears are used to turn the selected tube of mirrors to spin the kaleidoscopic beam around the optical axis. However, the rotatable mirror tubes cannot stencil patterns into the beam, which requires a pattern aperture in a focal plane of the projector. The beam of light may be conventionally patterned by a strip of film scrolled across the beam between opposite side spools.
U.S. Pat. No. 3,030,856 describes a kaleidoscope projector which forms variable apertures using a pair of main disks each supporting a plurality of smaller disks around its periphery. Each smaller disk has translucent apertures spaced regularly around its own periphery. The main disks and each of the smaller disks are simultaneously rotated to continuously, and practically uncontrollably, vary the effective aperture shape and the pattern of light in the beam projected from the kaleidoscope.
U.S. Pat. No. 4,232,359 describes an illumination system including a plurality of shutters having edges or patterns of desired shapes, one or more of which may be manually inserted into, and remain fixed at a respective location in, a beam of light.
U.S. Pat. No. 4,460,943 describes a light projector including a disc which has a number of openings for mounting "gobos" (stencils for light) and which is rotatable to insert a selected gobo into the focal plane of a beam of light.
However, none of the above prior art lighting systems provides multiple selectable and automatically positionable apertures together with means for rotating the selected aperture around the axis of a beam to controllably vary the projected pattern of light.